The present invention is directed to elongate intracorporeal devices, and particularly intraluminal devices for stent deployment, percutaneous transluminal coronary angioplasty (PTCA), and the similar procedures that are facilitated by an inflatable tubular member. PTCA is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient""s coronary artery and the balloon on the catheter is inflated within the stenotic region of the patient""s artery to open up the arterial passageway and increase the blood flow through the artery. To facilitate the advancement of the dilatation catheter into the patient""s coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced therein until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery. A balloon dilatation catheter may then be advanced through the guiding catheter into the patient""s coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient""s artery.
Once properly positioned across the stenosis, the balloon is inflated one or more times to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenosed region of a diseased artery. After the inflations, the balloon is finally deflated so that the dilatation catheter can be removed from the dilatated stenosis to resume blood flow.
Similarly, balloon catheters may be used to deploy endoprosthetic devices such as stents. Stents are generally cylindrical shaped intravascular devices that are placed within a damaged artery to hold it open. The device can be used to prevent restenosis and to maintain the patency of blood vessel immediately after intravascular treatments. Typically, a compressed or otherwise small diameter stent is disposed about an expandable member such as a balloon on the distal end of a catheter, and the catheter and stent thereon are advanced through the patient""s vascular system. Inflation of the balloon expands the stent within the blood vessel. Subsequent deflation of the balloon allows the catheter to be withdrawn, leaving the expanded stent within the blood vessel.
Typically, the distal section of a balloon catheter or other percutaneous device will have a radiopaque marker in order for the operator of the device to see it under x-ray or flouroscopy imaging. Generally, a band or ring of solid radiopaque metal is secured about an inner or outer shaft of a balloon catheter to serve as a radiopaque marker. Such a configuration, however, adds stiffness and discontinuity to the catheter shaft as the solid metal bands are relatively inflexible compared to a polymer balloon catheter shaft. What has been needed is a radiopaque marker for intracorporeal devices that adds little or no longitudinal stiffness to the device.
The invention is directed to a balloon catheter having an elongate shaft with a proximal section and a relatively short distal section. The distal section has a distal inner tubular member with a longitudinal axis, an outer surface and an inner surface. An inflatable balloon is disposed about the distal inner tubular member. A radiopaque marker made at least in part of a polymer has an outer surface which is substantially radially congruent with the outer surface of the distal inner tubular member from the longitudinal axis of the distal inner tubular member. An inside surface of the radiopaque marker can optionally be substantially radially congruent with the inside surface of the distal inner tubular member, or the inside surface of the radiopaque marker can be disposed between the inside surface of the distal inner tubular member and the outer surface of the radiopaque marker.
In one embodiment, the radiopaque marker can be a portion of the material of the distal inner tubular member which has been doped with a radiopaque material such as tungsten, bismuth, tantalum, barium, barium sulfate, compounds thereof or the like. In another embodiment, the radiopaque marker can be a separate discrete polymer member that is made of a radiopaque polymer or a radiolucent polymer doped with one or more radiopaque materials. The polymer of the radiopaque marker can be linear low density polyethylene, polyether block amide, alpha olefin copolymers, or the like, and can have a shore hardness or durometer selected so that the radiopaque marker and elongate inner tubular member which is axially coextensive with the radiopaque marker has a desired combined longitudinal stiffness. The combined longitudinal stiffness of the distal inner tubular member axially coextensive with the radiopaque marker and radiopaque marker can be selected such that it is substantially equal to or less than the nominal longitudinal stiffness of the distal inner tubular member axially adjacent the radiopaque marker.
Finally, two or more radiopaque markers as discussed above can be disposed along the distal inner tubular member. The radiopaque markers can be axially disposed at a proximal end of the inflatable balloon, a distal end of the inflatable balloon, at predetermined spacing to provide for a measuring function, or any other desired location or locations along the distal inner tubular member. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.